Prestressed drag shell construction or bucket



E. KALVE Nov. 14, 1967 PRESTRESSED DRAG SHELL CONSTRUCTION OR BUCKET Filed Nov. 2, 1964 INVENTOR. feA/ssr K4414:-

villi/7171111114 ATTORNEYS U ite 3,352,038 PRESTRESSED DRAG SHELL CONSTRUCTION R BUCKET Ernest Kalve, 1934 N. Hoyne, Chicago, Ill. 60647 Fiied Nov. 2, 1964, Set. No. 407,980 13 flaims. c1. 30-135 ABSTRAtIT OF THE DISCLOSURE This invention relates to improvements in dragscraper buckets and more particularly relates to the prestressing of dragscraper buckets.

Dragscraper buckets are generally of U-shape in plan defining an open scoop mouth. They are used in various types of excavation work where it is desired to excavate the material and pile the material onto a stable slope. These buckets are dragged along by a backhaul cable or drag line suitably connected to the open mouth ends of the bucket wall. The force exerted on the bucket by the backhaul cable, the weight of material, and the frictional resistance encountered by the bucket tend to warp and close the open ends of the bucket. In order to prevent this, prior dragscraper buckets are reinforced adjacent their open ends by yokes, crossbars or the like. Such reinforcing structures are undesirable because they limit the amount of material the buckets can handle and increase the weight of the buckets. Thus, known dragscraper buckets provide a relatively low payload to deadload ratio which is the ratio of the Weight of material the dragscraping bucket may handle to the weight of the empty dragscraper.

Therefore, it is an object of the present invention to provide a new and improved dragscraper bucket that eliminates crossbar reinforcing members and front reinforcing members that limit the payload of the dragscraper bucket while adding undesirable weight thereto.

Another object of the invention is to provide a new and improved dragscraper bucket that has a relatively high payload to deadload ratio.

A further object of this invention is to provide an improved dragscraper bucket prestressed such that buckling forces exerted on the bucket during normal operation thereof tend to neutralize the prestressing forces on the bucket.

Still another object of the present invention is to provide a novel dragscraper bucket having internal stresses there on which may be predetermined or adjusted in accord ance with the various materials to be handled and other load and stress requirements in or for the bucket.

It is still another object of the present invention to provide a new and improved method of and means for pre* stressing the dragscraper buckets.

Other objects, features and advantages of the present invention will be readily apparent from the following detailed description of certain preferred embodiments thereof taken in conjunction with the accompanying drawing, in which:

FIG. 1 is a top plan view of a dragscraper bucket constructed in accordance with the principles of the present invention;

tes Patent 0 3,352,638 Patented Nov. 14, I967 FIG. 2 is a side elevational view of the dragscraper bucket illustrated in FIG. 1;

FIG. 3 is a fragmentary enlarged cross-sectional view taken along line III-III of FIG. 2;

FIG. 4 is a partial top plan view of the bucket illustrated in FIG. 1;

FIG. 5 is a side elevational view of a modified dragscraper bucket constructed in accordance with the principles of the present invention; and

FIG. 6 is a fragmentary sectional detail view taken along line VI--VI of FIG. 5.

Referring to FIGS. 1 and 2, a dragscraper bucket 10 has a crescent-shaped body or shell 11 of generally U-shape in plan. The body 11 has an arcuate scoop wall 12, a relatively horizontal open bottom scraper blade surface 13, a declining open top surface 14 converging towards said bottorn surface, and an open front end 15 formed by spaced ends 16 which are free to flex resiliently relative to each other. Drag chains 17 are interconnected to each other at 19. A drag line or backhaul cable 20 is connected at 19 to the drag chains 17. The backhaul cable is suitably connected to a hoist (not shown) that winds the cable and drags the bucket 10.

By Winding the drag line 20 the bucket is dragged along the surface and gathers material therein. A force exerted on the line 20 in the direction of the arrow 21, opposite to the drag represented by arrow 21a exerts component forces 22 and 23 on the respective chains 17 that tend to warp or draw the free ends 16 together. Therefore, prior dragscraper buckets required heavy reinforcing members that prevented the ends of the bucket from flexing relative to each other.

According to the present invention, the scraper bucket 10 is prestressed (FIG. 4) such that a prestressing force 24 of a predetermined magnitude is placed on the scraper ends 16 to counteract or offset an external force 25 exerted on the scraper by the excavating or conveying of materials. Likewise, internal prestressing forces 26 and 27 are utilized to counteract external scraper forces 28 and 29. The magnitude of the prestressing forces 24, 26 and 27 is predetermined in accordance with the type and amount of material to be excavated by the bucket 10.

Referring to FIGS. 2 and 3, the bucket 10 is prestressed by a prestressing band 31. The prestressing band 31 has a larger circumference than the side wall 12 and is adapted to be spaced outwardly therefrom. The band 31 is suitably attached to the wall 12 and the ends 16 by stiffeners 32 and 33 welded around the body of the bucket. Outward, or external prestressing forces are exerted on the bucket 10 to expand band and/or bucket. Then the stiffeners 32 and 33 are welded to the prestressing band 31 at 34. After the welding is completed, the outward forces exerted on the bucket are released with the body of the bucket tending to regain its original shape and neutral position. However, the welded prestressing band 31 prevents the bucket from doing so and thereby permanently deforms and induces internal stresses 24, 26 and 27 in the bucket of a predetermined magnitude. The magnitude of the prestressed forces are such that the stresses placed on the bucket by excavating or conveying materials are neutralized or counteracted to a great extent by the prestressed forces 24, 25 and 27 to thereby return the bucket to its neutral position when it is excavating and thus eliminate the need for material-limiting and weight increasing reinforcing cross bars.

Referring to FIGS. 5 and 6, there is illustrated another dragscraper bucket 35 having a similar configuration as the dragscraper bucket 10 with a crescent side wall 36, an opened bottom surface 37, and an open top surface 38. However, the dragscraper 35 has an arcuate cross-section housing 39 welded to the side wall thereof at welds 4i) and attached to the ends 41 of the bucket. The bucket 35 has a top arcuate prestressing band 42 attached by stiffeners 43 to the bucket and a bottom crescent or arcuate prestressing band 44 attached by stiffeners 45 to the outer surface of the side wall 36 below the housing 39. The prestressing bands 42 and 44 operate to maintain the bucket in a prestressed condition.

The housing 39 extends centrally around the outer surface of the bucket and the bands 42 and 44 extend around the bucket 10 and have their ends fastened to the bucket adjacent the housing ends and the bucket ends 41. The bands 42 and 44, as illustrated in FIG. 4, branch-out from the housing 39. The bands 42 and 44 and their respective stiifeners 43 and 45 have a cross-section similar to the band 31 and stiffeners 32 and 33 (FIG, 3).

A prestressing cable 46 is located within the housing 39 and has its ends 47 suitably attached adjacent the housing ends 41 by suitable anchoring means 48. The prestressing cable is tensioned to a predetermined magnitude such that internal stresses are placed on the bucket 35. The tensioned prestressing cable 46 and the prestressing bands 42 and 44 are attached to the bucket after the bucket is expanded such that internal stresses induced or placed upon the body of the bucket by such expansion are maintained by the cable 46 and the bands 42 and 44. (The tension cable 46 and the bands 42 and 44, when attached at the ends of the bucket 35, tend to apply forces to the ends 41 of the bucket 35 that urge the ends 41 in opposite directions away from each other.)

It is of course understood that prestressing cables 46 may be utilized with the bucket 10 (FIG. 3) by utilizing the prestressing band 31 and stiffeners 32 and 33 as a housing for said cable, as illustrated in FIGURE 3, with the prestressing band 31 either acting in conjunction with the cable or merely acting as a cover for the cable. Likewise, the prestressing bands 42 and 44 utilized in FIG- URE 3 may also include prestressing cables 46 and/or further, may be utilized in the bucket 10 in conjunction with the prestrsesing band 31.

Of course, suitable means may be attached to the prestressing cable 46 for tightening or tensioning the prestressing cable 46 a predetermined amount while it is attached to the bucket. Thus, the cable may be used to adjust the stress placed on the bucket 35.

In this manner, I have provided a dragscraper bucket which is of relatively lightweight and has a high payload to deadload ratio.

Although minor modifications might be suggested by those skilled in the art, it should be understood that I wish to embody within the scope of the patent warranted hereon all such embodiments as reasonably and properly come within the scope of my contribution to the art.

I claim as my invention:

1. A dragscraper bucket comprising:

a generally crescent-shaped wall defining an open bot tom and a front opening;

a prestressing band spaced from the periphery of said wall; and

means attaching said band to said periphery and stressing said wall from a neutral position to a normal prestressed position wherein the ends of said wall are urged apart to a predetermined extent such that under load stresses placed on the bucket are substantially neutralized whereby toenable the bucket to be used without cross-bar yoke means between the front ends of said wall.

2. A drags'craper bucket comprising: I

a generally crescent-shaped wall defining an open bottom and a front opening;

a plurality of peripheral prestressing bands attached to the periphery of said wall;

means attaching said bands to said periphery to stress said wall from a neutral position to a normal prestressed position wherein the ends of said wall are urged apart to a predetermined extent such that under load stresses placed on the bucket are substantially neutralized whereby to enable the bucket to be used without cross-bar yoke means between the front ends of said wall.

3. A dragscraper bucket of generally U-shape comprismg: i

a pair of spaced side walls defining an open bottom and a front opening;

a prestressing cable attached about the periphery of said walls and stressing said walls from a neutral position to a stressed position wherein the walls are urged in opposite directions away from each other.

4. A dragscraper bucket comprising:

a generally crescent-shaped wall having a pair of spaced ends forming a front opening;

a generally crescent-shaped band having a larger diameter than said wall; and

means interconnecting said band about the periphery of said wall to stress said wall and increase the distance between the ends thereof from a neutral position to a stressed position and such that the bucket is adapted to be used without reinforcing cross-bar yoke means between the front ends of the wall because the stresses placed on the bucket under load are substantially neutralized.

5. A dragscraper bucket comprising:

a pair of spaced side walls having an open bottom surface;

a plurality of arcuate bands; and

means attaching said bands about the periphery of said walls to stress said walls and increase the distance therebetween from a neutral position of a stressed position and such that the bucket is adapted to be used without reinforcing cross-bar yoke means between the front ends of the wall because the stresses placed on the bucket under load are substantially neutralized.

6. A dragscra-per bucket comprising:

a crescent-shaped wall having a pair of spaced ends defining a front opening;

a stressing cable being attached adjacent said wall ends and about the periphery of said wall; and

said stressing cable being attached to said wall and being tensioned a predetermined amount such that said cable normally maintains said wall in a prestressed position with the wall ends being urged away from each other.

7. A scraper bucket structure comprising:

a generally U-shaped metal plate wall structure including forwardly extending spaced side walls defining a forward opening and being free to flex resiliently relative to one another,

means for connecting the front portions of the walls to a drag line tending to flex the side walls toward one another under dragging load, and

means normally prestressing said side walls away from one another to an extent which will resist flexing of the side walls into neutral load-force relation toward one another until predetermined drag line load is imposed on the side walls.

8. A method of manufacturing a prestressed dragscraper bucket having side wall portions, comprising:

flexing the side wall portions of the bucket apart from a neutral position to a prestressed position, and attaching prestressing means about the periphery of the bucket and maintaining said bucket in the prestressed position to resist return of the side walls to said neutral position under drag load.

9. A method of manufacturing a prestressed dragscraper bucket having side wall portions, comprising:

placing a prestressing band to the periphery of the dragscraper bucket,

simultaneously flexing the prestressing band and the bucket such that the bucket is prestressed to spread said side wall portions apart a predetermined amount from a neutral position to a prestressed position such that the stresses placed on the bucket by loading in use are substantially neutralized, and attaching the band to the bucket to maintain the bucket in the prestressed position to resist return of the side walls to said neutral position under full drag load. 10. A method of manufacturing a prestressed dragscraper bucket comprising:

flexing the bucket from a neutral position to a pre stressed position, and attaching a tensioned cable to the ends of the bucket and about the periphery of the bucket to maintain said bucket in a normal prestressed position. 11. A dragscraper bucket of generally U-shaped comprising:

a pair of spaced side walls defining an open bottom and a front opening; means prestressing said bucket such that front end portions of said side walls are norm-ally urged in opposite directions away from each other out of neutral position such that stresses placed on the bucket in dragging use thereof are substantially neutralized; and means for attaching drag lines to said front end portions of the side walls tending under drag loads to draw said front end portions toward said neutral position. 12. A dragscraper bucket of generally U-shape comprising:

a pair of spaced side walls defining an open bottom and a front opening free from any cross-bar between the front end portions of the walls; and

stressing means attached to said walls, and said stressing means urging the Walls in opposite directions away from each other and from a neutral position such that stresses placed on the bucket by drag loads are substantially neutralized.

13. A dragscraper bucket of generally U-shape comprising:

a pair of spaced side Walls defining an open bottom and a front opening; and

a stressing band attached to the side walls of said bucket, said band providing said side walls with internal stress forces of a predetermined magnitude that urge the side walls normally apart to a predetermined extent from a neutral position thereof such that stresses placed on the bucket in dragging use are substantially neutralized to thus eliminate any need for cross-bar reinforcing yoke means between the front end of the side walls.

References Cited UNITED STATES PATENTS 1,741,167 12/1929 Smith 37-147 X ABRAHAM G. STONE, Primary Examiner.

A. E. KOPECKI, Assistant Examiner. 

1. A DRAGSCRAPER BUCKET COMPRISING: A GENERALLY CRESCENT-SHAPED WALL DEFINING AN OPEN BOTTOM AND A FRONT OPENING; A PRESTRESSING BAND SPACED FROM THE PERIPHERY OF SAID WALL; AND MEANS ATTACHING SAID BAND TO SAID PERIPHERY AND STRESSING SAID WALL FROM A NEUTRAL POSITION TO A NORMAL PRESTRESSED POSITION WHEREIN THE ENDS OF SAID WALL ARE URGED APART TO A PREDETERMINED EXTENT SUCH THAT UNDER LOAD STRESSES PLACED ON THE BUCKET ARE SUBSTANTIALLY NEUTRALIZED WHEREBY TO ENABLE THE BUCKET TO BE USED WITHOUT CROSS-BAR YOKE MEANS BETWEEN THE FRONT ENDS OF SAID WALL. 